AOFAR Compass AF-4580

1. Components Name

• 1. Lid
• 2. Window with Aiming line
• 3. Hinge
• 4. Arrow No1
• 5. Scale (Centimeter Ruler on opposite side)
• 6. 360° Rotating Bezel
• 7. Heavy-duty zinc Die-Cast
• 8. Spirit level
• 9. Holding Ring
• 10. Glow-in-the Dark Circle (Fixed tip point)
• 11. Glow-in-the Dark Arrow No2
• 12. 360° compass card (Thermoelastic Liquid-Filled Capsule with Floating Dial)
• 13. Tripod Connection
• 14. Aiming Point
• 15. Sighting Lens with Adjustable Diopter
• 16. Conversion chart: Angle /Gradient/Distance
• 17. Distance-measuring notches

2. Product Specification

The compass consists of a Zinc alloy housing and a metal lid with a glass window featuring an aiming line etched into it. The window is attached to the compass housing by a vertical spring holder, allowing approximately 3mm of vertical movement via a screw.

The window is mounted in the lid with a robust hinge that can turn 180°, enabling the window to be moved into a reading position and folded back after use.

The compass is equipped with an integrated spirit level.

It can be screwed onto a tripod via a threaded fitting in the base, serving as a theodolite for simple terrain surveys.

This lens system, with an integrated index line and magnifier, allows for extremely precise readings. Mirror reading and potential parallax errors are eliminated by prismatic reading. The dial system's excellent damping ensures rapid and precise readings to the fraction of a degree.

3. Use Tips

Adjust the lid (1) up or down until the Aiming Point (14), aiming line (2), and the object are aligned on a straight line. Maintain the compass horizontally using the integrated spirit level (8).

Skillfully handling the compass ensures the aiming line (2) corresponds to the Aiming Point (14), aligning the eyes, compass dial, and object for utmost accuracy. This method allows reading the fraction of an angular degree.

Adjust the prism or lens on the 360° Rotating Bezel Ring (6) until the numbers on the compass card (12) are clearly visible. For models with an adjustable eyepiece, rotate the Sighting Lens (15) until the degree numbers are clearly visible.

Optimal results are achieved when the compass is held 1-2cm from the eyes.

4. Taking a Bearing

In the reading position, aim at an object using the Aiming Point (14) and aiming line (2). Read the marching direction value on the compass card (12), which also corresponds to the object's azimuth.

5. Walking a Given Bearing or Direction of Travel

When the bearing is known, look at the compass card (12) and turn your body until the known bearing is visible on the dial. The sighting line will then intersect the object.

6. Orienting the Map

For complex operations on a topographic map, orientate the map's geographic north with the Earth's magnetic north.

Place the compass on the map. Align the centimeter-marked line (5) with the meridian closest to your position, so the upper lid (1) points to the map's north. Meridians are parallel lines running from the top to the bottom of the map.

Hold the compass in position and rotate the map until the north-seeking needle (11) on the dial coincides with the index line of the Glow-in-the Dark Circle (10). The map is now oriented with the ground. Magnetic declination has not been accounted for.

7. Determining the Direction of Travel on the Map

1. After aligning the map with the north pole (as described in point 6), draw a line on the map from your position to your final destination.
2. Place the compass on the map with one edge along the line from your position to the objective. The compass lid indicates the direction of the objective.
3. Read the marching direction value on the compass card (12) corresponding to the index line of the Glow-in-the Dark Circle (10).
4. Remove the compass from the map. Look at the compass card (12) and turn around until the value of your marching direction (defined as point C) is visible.
5. Find an auxiliary destination point on the same survey line and start following it.
6. Repeat this operation until you reach your final destination. This process helps maintain the defined direction over longer routes.

8. Determining Your Own Position in the Field

Select two visible points on the ground and mark them on the map. Once the map is oriented (as per point 6), use the compass to measure the position value (A) in degrees. Draw a line on the map according to this value, then pass through point (B).

[Diagram showing a compass on a map with points A and B and a north arrow]

9. Estimate the Distance on the Map

Measure the distance to the object on the map using the Centimeter Ruler (5) and multiply by the map's scale.

Map Scale 1:25000
Distance (M) = Distance (mm on map) x 25000 / 1000

Map Scale 1:50000
Distance (M) = Distance (mm on map) x 50000 / 1000

10. Measuring Angles

Measure the right side of the object. Note the value in degrees. Slowly orientate the compass towards the left side of the object. Deduct the second value from the first value in degrees. The difference represents the angle between the left and right sides of the object.

Note: When measuring angles relative to north, if the 360° (north) line crosses the direct line on the Glow-in-the Dark Circle (12) during measurement, consider 360° = 0°. The calculation will be 360° - second value in degrees + first value in degrees.

Example: If the first value is 4° and the second is 354°, the angle is 10° (360 - 354 + 4 = 10).

TABLE FOR CALCULATE

11. Measure the Distance on the Ground

Using the principles from points 9 and 10, you can determine the distance on the ground between two visible points.

For example, measure the width of a farmhouse or the length of a bridge. A necessary condition is that the line from your position to the object must be as perpendicular as possible to the side of the object being measured.

Example: A bridge spans a river at a distance of 4000m, transverse to the line of vision. If an angle of 6° is measured from the right to the left river bank, the bridge length is 10% or 1/10.

Calculation: 4000m x 10% = 400m OR 4000m x 1/10 = 400m.

[Diagram illustrating a river, a bridge, and measurement lines]

12. Determining the Distance to an Object of Known Width

If the height or width of an object is known or drawn on a map, its distance can be determined by inverting the calculations from points 9, 10, and 11. If the width of an object corresponds to an angle of 8° and is 1/7 of the distance (according to Table 2), the distance is 7 times the width or height.

Example: The angle measured between objects B and C is 34°. The distance between B and C is 5 km according to the map. Column IV, Table 2 indicates 66%.

Calculation: (100% / 66%) x 5km = 7.5km OR 5km x 3/2 = 7.5km.

When using this method, the object of known width must be perpendicular to the line of sight.

[Diagram showing points B and C on a map with a distance of 5km]

13. Determining the Distance with Scale-Marked Glass

1. Aiming line
2. Horizontal line with measuring notches
3. Measuring line
4. First object
5. Second object

The glass cover with aiming lines has notches for measuring the distance to an object. The distance between the target and another visible object on the same level as the observer is measured on the horizontal line of the glass.

10 notches = 0.9cm; each notch = 1/9cm. The distance between eyes and the Aiming line is 12cm.

Example: If the distance between two objects is 36m and there are 12 notches on the glass.

Calculation: (12cm / 0.09cm) x (12 / 2) = 400m. This is the distance between you and the object.

The simple formula is: (1200 x 36m) / (9 x 12) = 400m.

If the distance between two objects is 36m, there are 12 notches on the glass, and another object is at a distance on the same level with 18 notches, the calculation is: 36m / 12 * 18 = 54m.

[Diagram showing a scale-marked glass with aiming lines and notches]

14. WARNING!

In high-quality compasses, needle oscillation is stabilized by the liquid it is immersed in. Significant temperature or pressure variations can cause small air bubbles around the compass card. These bubbles do not affect functioning and will disappear within 24-48 hours under normal temperature conditions.

Avoid using the compass at temperatures below 0°C.

Keep the compass away from magnetic fields generated by iron parts, magnetic cores, or electric wires, as these can cause inaccurate readings.

Protect your instrument from falls or damage and do not tamper with it to maintain the guarantee.

15. Contact Us

Email: info@aofar.com, service@aofar.com, engineer@aofar.com

URL: www.aofar.com